1. Field of the Invention
The present invention relates to a method for adjusting an image pickup luminance, and in particular, to an adjusting method of flash intensity for a flash lamp.
2. Related Art
A flash lamp is disposed in a digital image capture apparatus to compensate for an insufficient luminance for an object to be shot during shooting. In other words, when the object to be shot is in an environment with a low luminance, the digital image capture apparatus triggers the flash lamp during shooting, so as to enable the luminance of a shot digital image corresponding to the object to achieve a desirable value through a strong flash light emitted by the flash lamp.
Generally, the digital image capture apparatus performs a pre-flash to emit a pre-flash light before emitting a main-flash light. The digital image capture apparatus evaluates a flash intensity (also referred to as an output intensity) of the main-flash light according to the luminance of the image corresponding to the object shot under the pre-flash light.
Moreover, a shooting mode of the digital image capture apparatus is substantially classified as a normal mode (e.g., a portrait mode, a landscape mode, etc.) and a macro mode. The digital image capture apparatus uses pre-flash lights with different flash intensities to evaluate the flash intensity of the main-flash light in different shoot modes.
In the normal mode, the digital image capture apparatus is far away from the object to be shot, so the digital image capture apparatus uses a pre-flash light with a greater flash intensity. In the macro mode, the digital image capture apparatus is close to the object to be shot, so the digital image capture apparatus generally uses a pre-flash light with a smaller flash intensity.
When the digital image capture apparatus is close to the object to be shot, if the normal mode is set, the image corresponding to the object and retrieved under the main-flash light has an over exposure since the excessive high flash intensity of the pre-flash light causes the main-flash light to have an excessive high flash intensity.
When the digital image capture apparatus is far away from the object to be shot, if a macro mode is set, the image corresponding to the object and retrieved under the main-flash light has an insufficient exposure since the excessive low flash intensity of the pre-flash light causes the main-flash light to have an excessive low flash intensity.
However, a user may not always switch to a corresponding shoot mode as the actual circumstance requires. If a pre-flash is carried out by a pre-flash light with an incorrect flash intensity, the flash intensity of the main-flash light evaluated by the digital image capture apparatus may become inaccurate accordingly. As such, the digital image capture apparatus tends to shoot an over bright or over dark digital image.